1. Field of the Invention
The present invention relates to a motor-operated valve for controlling the flow rate of a refrigerant for an air conditioner and, more particularly, to a canned gear motor-operated valve provided with a gear reduction mechanism in a can, which is a gastight vessel.
2. Description of the Related Art
It is known that motor-operated valves, which are opened and closed via an electric motor, are broadly divided into two types. A first type is a type in which the valve is opened and closed by directly transmitting the rotation of a rotor to a screw mechanism, and is disclosed, for example, in Patent Reference 1. A second type is a type in which the valve has a reduction gear apparatus for transmitting the rotation of the rotor to the screw mechanism while reducing the speed, and is disclosed, for example, in Patent References 2 and 3.
[Patent Reference 1] Japanese Patent Laid-Open No. 2000-356278
[Patent Reference 2] Japanese Patent Laid-Open No. 2002-84732
[Patent Reference 3] Japanese Patent Laid-Open No. 2003-232465
The motor-operated valve of the first type has a relatively compact configuration, but has a disadvantage that the application thereof is limited to a case where the load is low, and it is difficult to increase the resolution of valve opening per one drive pulse.
The motor-operated valve of the second type can be used even in a case where the load is high and can be configured so that the resolution of valve opening per one drive pulse is increased, but has a problem in that the size of the whole of the motor-operated valve is increased because a gearbox for a reduction gear apparatus is provided separately from a motor section.
An object of the present invention is to provide a motor-operated valve suitable for accommodating a reduction gear apparatus in a small space in a rotor in a compact manner.